The major objective of the current research is to determine whether hormones act at one, or more than one, control sites when interacting with the motor circuits that control a particular behavior. This is being studied within the context of behavioral and pharmacological studies which demonstrate effects of egg-laying hormone (ELH) and serotonin (5-HT) on feeding behavior in Pleurobranchaea and Aplysia. The effect of ELH and 5-HT on feeding muscles and neuronal circuitry controlling them will be investigated. In addition, the underlying biochemical and biophysical mechanisms of action of observed effects will be investigated, including the involvement of adenylate cyclase.